The present invention relates to an optical sensor unit adapted to be used in detecting precisely a position, a shape, a transfer speed, etc of the papers such as a bank note, a printing paper and the like which are transferred in a cash dispenser, a duplicating machine and the like.
The prior art optical sensor unit comprises a light emitting element and a light receiving element positioned opposite the emitting element while a transfer path composed of two transfer guides for guiding the papers is interposed between the light emitting element and the light receiving element for detecting the position, the shape transfer speed, etc. by measuring quantity of light received by the light receiving element which is varied in the company of the papers on the transfer path.
The arrangement of the prior art optical sensor unit will be described more in detail.
The light emitting element and the light receiving element composed of respectively LED, etc. are soldered on a printed circuit board and fixed thereto. The printed circuit board having a previously printed wiring pattern thereon is capable of connecting the light emitting element to the light receiving element by soldering a signal line of the external equipment on the printed circuit board. The printed circuit board is fixed to the transfer guides forming the transfer path by screwing a bracket fixed to the cash dispenser or the duplicating machine etc.
The light emitting element is housed in a rubber cylinder provided between the transfer guides and the printed circuit board to prevent dust, paper dust etc. attached to the papers from attaching to an optical element. The transfer guides have holes closed by transparent glasses and positioned with the optical sensor unit so as to transmit and receive the light of the optical sensor unit.
The light receiving element has same structure as the light emitting element and is positioned opposite the light emitting element so that both optical axes are aligned with each other.
There are following problems in the prior art optical sensor unit.
Firstly, the rubber tube is slightly pressed toward the transfer guides to prevent the optical sensor unit from being blocked by the dust, paper dust, etc. However, an impact resilience force generated by the pressing operation of the rubber tube toward the transfer guides makes the printed circuit board fixing the optical sensor unit (composed of light emitting and receiving elements) flexible whereby the optical axis of the light emitting element does not align with that of the light receiving element, namely, the axes are displaced with respect to each other. As a result, the light emitted from the light emitting element can not be accurately received by the light receiving element, which results in generating an erroneous operation. Accordingly, the fixing position of the bracket or the length of the rubber tube are required to be considerably accurate to obtain an appropriate pressing force of the rubber tube toward the transfer guides without displacing the optical axes of the optical sensor unit.
Furthermore, since the signal line from the exterior apparatus is directly soldered on the printed circuit board, it is difficult to detach the signal line from or attach the signal line to the bracket, which is liable to cause breaking of the signal line.
Still furthemore, it involves difficult work to exchange the optical sensor unit with another optical sensor unit since the signal line of the exterior apparatus is fixed and the printed circuit board is fixed to a bracket by the screw.